Upright extraction cleaning machines have been used for removing dirt from surfaces such as carpeting, upholstery, drapes and the like. The known extraction cleaning machines can be in the form of a canister-type unit as disclosed in U.S. Pat. No. 5,237,720 to Blase et al. or an upright unit as disclosed in U.S. Pat. No. 5,500,977 to McAllise et al. and U.S. Pat. No. 4,559,665 to Fitzwater.
The state of the art for water extraction cleaning machines utilizes one of two different technologies. First, water is mixed with a cleaning detergent and the resulting solution is sprayed onto the surface to be cleaned. The detergent includes chemical agents adapted to enhance the cleaning performance and dirt attraction of the cleaning solution. The vacuum motor is used to create a source of suction for withdrawing the cleaning solution and entrapped dirt back into the cleaning machine.
A more recent development in the water extraction cleaning industry is the use of steam as the cleaning agent. The cleaning machine incorporates a boiler or other means for generating steam. The steam is pumped to an applicator where it is brought into contact with the surface being cleaned. The steam systems have the advantage of creating a temperature which effectively kills a wide range of microbes, bacteria, microorganisms, and mites. However, the steam systems suffer from poor cleaning performance. Additionally, the high power requirement for generating steam does not allow ample remaining power for running a vacuum motor, so cleaning performance is further hindered. Conversely, conventional detergent cleaning systems are somewhat effective at cleaning surfaces, but could be made more effective by raising the temperature of the cleaning solution to some point below the boiling point. There is an optimal temperature at which cleaning performance is maximized without causing damage to carpets or setting stains. This temperature is around 150 degrees Fahrenheit.
The Chae et al. U.S. Pat. No. 5,502,872 discloses an electric vacuum cleaner having a steam discharge and cloth wiper. A water tank mounted on the handle dispenses water into an aspirator which atomizes the water into a stream of pressurized air from an impeller exhaust and then heats the atomized water to steam before discharging the steam/air mixture onto a surface to be cleaned.
The Jones et al. U.S. Pat. No. 4,114,229 discloses a surface cleaning apparatus in which a cleaning fluid is heated in a conduit in a control casing and then sprayed onto a surface to be cleaned. A suction nozzle in a base unit removes dirty water from the surface.
The Parise et al. U.S. Pat. No. 4,046,989, and Putt, U.S. Pat. No. 3,699,607, disclose floor-cleaning equipment in which a cleaning fluid is heated before it is sprayed onto a surface to be cleaned. Both systems appear to heat the cleaning fluid in a tank.
When heated cleaning fluid is applied to a surface that is at ambient temperature, the cleaning fluid is cooled by the carpet, thus decreasing the cleanability of the applied fluids. Heating the cleaning fluid to a higher temperature to compensate fir the surface cooling may overcome this problem, but with an increase in energy required for the operation.
Sometimes, one encounters spots on a carpet or other surface to be cleaned that have a stain or other difficult area to clean while conduction an ordinary cleaning process. Typically, the user must repeat the extraction process in a particular spot with limited success.
DE 195 22 893, published 8 Feb. 1996, discloses a canister extraction cleaning machine in which a cleaning solution can be heated in a high speed in line heater to a temperature below boiling or above boiling for application to a floor with a wand. This publication further discloses in another embodiment a canister extraction cleaning machine that has a solution supply for application of unheated solution onto a surface to be cleaned through a wand and further has a separate tank with a heater for heating water to steam. The separate tank is connected to the wand to deliver steam to the wand with or without cleaning solution.